The present invention relates to a battery pack, and more particularly, to an improvement in a structure for grounding a terminal cover used as a shield for a battery pack.
Hybrid vehicles and electric vehicles use high voltage battery packs as power sources. Such a battery pack is connected to a high voltage unit of a vehicle by connecting a connector or a round terminal to a terminal base arranged on the battery pack.
A high voltage portion of the battery pack produces electromagnetic noise. Thus, high voltage cables connected to the battery pack are provided with shields. Furthermore, the main body of the battery pack, which accommodates a battery, is covered by a metal case, which is grounded to function as a shield.
The terminal base includes terminal connection portions connected to a connector or round terminal. The terminal connection portions forms a shield interruption in the battery pack. That is, the terminal connection portions form an interruption between the shield of the high voltage cables and the shield of the battery pack main body. By using a connector having an internal structure for connecting the shield of a high voltage cable to the shied of the battery pack main body, the problem of shield interruption at the connection portion can be solved. However, a round terminal has a simple structure and does not include a shield. As a result, electromagnetic noise may leak out of the terminal connection portion.
Accordingly, in the prior art, to prevent the leakage of electromagnetic noise, as shown in FIG. 1, a case 100 for a battery pack main body includes a terminal base 101, which is covered by a metal terminal cover 102. High voltage cables 103 and 104 have distal ends respectively provided with round terminals 105 and 106, which are connected to terminal connection portions 107 and 108 arranged on the terminal base 101. The terminal cover 102 covers the terminal connection portions 107 and 108. FIG. 2 shows the cross-sectional structure of the portion near the terminal base 101. The terminal cover 102 is directly attached to the case 100 of the battery pack main body and grounded via the case 100. Thus, the terminal cover 102 prevents the leakage of electromagnetic noise from the terminal connection portions 107 and 108 of the terminal base 101.
A battery pack may be provided with a high voltage interlock (HVIL) switch, which is arranged on the terminal base. The HVIL switch disconnects the terminal connection portions from the battery when removing the terminal cover. The HVIL switch is one type of a safety device that prevents the application of high voltage to the terminal connection portions of the terminal base that are exposed when the terminal cover is removed. When installing the HVIL switch to the terminal base, stable opening and closing of the switch in accordance with the removal and attachment of the terminal cover must be ensured. Thus, as shown in FIG. 3, a plug 111 is arranged in a terminal cover 112 to open and close the HVIL switch, which is arranged on a terminal base 109. Accordingly, the terminal cover 112 is directly attached to the terminal base 109 on which the HVIL switch 110 is arranged and not to the case 100 of the battery pack main body. In this case, referring to FIG. 4, which shows the cross-sectional structure of the portion near the terminal base 109, the terminal cover 112 does not come into direct contact with the case 100 of the battery pack main body.
Furthermore, to protect the terminal connection portions from moisture, the terminal cover may be provided with a seal. In such a case, to seal the terminal base with the terminal cover, the terminal cover must be directly attached to the terminal base.
In this manner, in a structure in which the terminal cover is attached to the terminal base and not to the case of the battery pack main body, the terminal cover and case cannot be electrically connected, and the terminal cover cannot be grounded. Thus, sufficient shielding of the terminal connection portions cannot be ensured.
Japanese Laid-Open Patent Publication No. 2003-115679 describes a grounding structure for a printed circuit board accommodated in a conductive case. In the publication, a grounding plate, which is arranged on an attachment boss of the printed circuit board, electrically connects the case and printed circuit board. This grounds the printed circuit board. However, such a grounding structure cannot be used as the grounding structure for the above-described battery pack terminal cover.